Many metal detectors include various oscillatable controls which may be preset as desired according to the type of metal detecting operation to be carried out. Some metal detectors include a discriminating adjust switch provided with an oscillatable rotary control knob and the discriminating adjust switch is utilized to discriminate between different types of metals detected by the detector. In locations in which metal can pull tabs may be expected, many operators of metal detectors may set the discriminating switch high enough to reject these pull tabs. However, setting the discrimination switch sufficiently high to reject the pull tabs may render the detector useless in locating small gold, nickel and medium gold items. Accordingly, a person using a metal detector must constantly change the discriminating adjust switch if he is to be able to determine the likelihood of the type of metal detected by the detector.
Assuming that the operator of a detector sets the discriminating adjust switch in the first position, all desirable precious metals will be indicated as well as undesirable pull tabs. If metal is detected, the operator may then adjust the discriminating adjust switch to the second position which will prevent the detector from indicating the presence of precious metals but will enable the detector to continue to indicate the presence of a pull tab. If the signal is still retained with the discriminating adjust switch in the second position, then the operator can move the discriminating adjust switch to the third position. This position will reject a common pull tab. However, if the signal is still retained, there is a probability that the target might be a copper or silver coin. The operator can then move the disciminating adjust switch to the fourth position and to determine if the opject is a copper or silver coin or possibly an aluminum screw cap. The number four position will reject the screw cap and retain the signal on copper and silver coins. Accordingly, proper operation of the discriminating adjust switch is important in saving time and allowing the operator of the detector to dig only for those metals which he is seeking.
However, most metal detectors include a discriminating adjust switch which is remote from the handle of the detector and which thus must be operated by the other hand of the operator. This continuous two-hand operation can be become very tiring. Accordingly, a need exists for a metal detector including a discriminating adjust switch but whereby the discriminating adjust switch may be operated by the hand of the user of the detector from which the detector is supported.
Examples of various different forms of trigger controls and other adjustment structures associated with a handle are disclosed in U.S. Pat. Nos. 2,502,626, 3,549,985, 3,591,740, 3,649,793, 3,711,666, 3,742,341 and 3,875,498. However, these previously known devices are not specifically adapted for use on a metal detector for actuation by the digit of a hand from which the metal detector is supported.